In particular, I think “The above line is Dip's way of letting you know that you've created a function called greet” moves too fast, even if your beginners have math training. It likely won’t be clear to beginners that this is similar to functions in mathematics, and it introduces too many new things (what’s that -> about? What is print?)
I would teach users about variable assignment and reassignment (assuming those can be done from the REPL, but if they can’t, fix that first) before introducing functions. That way, you can introduce functions as helping against having to repeatedly type the same characters.
You probably can find a way to introduce print before functions, too (e.g. as a way to show multiple items on a single line)
The suggestion to sit with absolute beginners going through the tutorial is great. I expect it would uncover tripping points you aren’t aware of.
Edit: I also think using a calculator as the example program isn’t a good choice. New users already have a better calculator the moment they start the REPL.
I have seen "start coding in a day" courses, that used Python (a robust language) to teach complete beginners from scratch.
In fact, I once attended a demo of a scholastic programming courseware app that had most of the people in the room (primarily K-12 teachers in their 30s) doing "Hello World" Python apps in about fifteen minutes, and understanding what they did, in about half an hour.
It was all in the presenter and the design of the site.
I have no idea if the app ever took off. That was about three years ago.
That program teaches variable assignment, loops, conditionals, mathematical comparisons, input and output. It teaches the difference between numbers and strings too. But it’s also a short program, fun to play, and easy enough for people to hack so they can alter stuff on there to subtly change its behaviour (eg the messages printed to screen, the range of numbers randomly generated, etc).
I’ve had good success using that program for a range of different age groups and capabilities.
Edit: just to add, we would cover the basics about variables etc first before moving on to that game. But that would be the first “useful” program they’d write.
I'm not a beginner, so maybe I'm wrong here, but it doesn't look that much simpler than python to me.